/*
 * $Id: GolombBuffer.cpp 20 2012-04-20 01:42:55Z aleksoid $
 *
 * (C) 2006-2012 see Authors.txt
 *
 * This file is part of MPC-BE.
 *
 * MPC-BE is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * MPC-BE is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */


#include "stdafx.h"
#include "GolombBuffer.h"

CGolombBuffer::CGolombBuffer(BYTE* pBuffer, int nSize)
{
	m_pBuffer	= pBuffer;
	m_nSize		= nSize;

	Reset();
}

UINT64 CGolombBuffer::BitRead(int nBits, bool fPeek)
{
	//	ASSERT(nBits >= 0 && nBits <= 64);

	while (m_bitlen < nBits) {
		m_bitbuff <<= 8;

		if (m_nBitPos >= m_nSize) {
			return 0;
		}

		*(BYTE*)&m_bitbuff = m_pBuffer[m_nBitPos++];
		m_bitlen += 8;
	}

	int bitlen = m_bitlen - nBits;

	UINT64 ret = (m_bitbuff >> bitlen) & ((1ui64 << nBits) - 1);

	if (!fPeek) {
		m_bitbuff &= ((1ui64 << bitlen) - 1);
		m_bitlen = bitlen;
	}

	return ret;
}

UINT64 CGolombBuffer::UExpGolombRead()
{
	int n = -1;
	for (BYTE b = 0; !b; n++) {
		b = (BYTE)BitRead(1);
	}
	return (1ui64 << n) - 1 + BitRead(n);
}

INT64 CGolombBuffer::SExpGolombRead()
{
	UINT64 k = UExpGolombRead();
	return ((k&1) ? 1 : -1) * ((k + 1) >> 1);
}

void CGolombBuffer::BitByteAlign()
{
	m_bitlen &= ~7;
}

__int64 CGolombBuffer::GetPos()
{
	return m_nBitPos - (m_bitlen>>3);
}

void CGolombBuffer::ReadBuffer(BYTE* pDest, int nSize)
{
	ASSERT (m_nBitPos + nSize <= m_nSize);
	ASSERT (m_bitlen == 0);
	nSize = min (nSize, m_nSize - m_nBitPos);

	memcpy (pDest, m_pBuffer+m_nBitPos, nSize);
	m_nBitPos += nSize;
}

void CGolombBuffer::Reset()
{
	m_nBitPos	= 0;
	m_bitlen	= 0;
	m_bitbuff	= 0;
}

void CGolombBuffer::Reset(BYTE* pNewBuffer, int nNewSize)
{
	m_pBuffer	= pNewBuffer;
	m_nSize		= nNewSize;

	Reset();
}

void CGolombBuffer::SkipBytes(int nCount)
{
	m_nBitPos  += nCount;
	m_bitlen	= 0;
	m_bitbuff	= 0;
}
